(a) Field of the Invention
The present invention relates to a multi-set switched DC electric machine having conduction ring and brush, driven by the DC power source or by the DC power source rectified from the AC power source, and having the rotary part of magnetic force actuated electric machine being installed with an auxiliary excitation winding set, for being connected in series with a magnetic field winding set of electric machine of another electric machine through the auxiliary excitation winding set installed on the rotary part of magnetic force actuated electric machine, such that the excitation can be variable through altering the current of the magnetic field winding set of electric machine of the another electric machine thereby changing the operational characteristic of the electric machine.
(b) Description of the Prior Art
A conventional switched DC electric machine having conduction ring and brush, e.g. a switched electric machine having conduction ring and brush and having permanent magnetic pole or having reluctance rotor, often utilizes a Hall element for sensing locations so as to determine the switch timing, or utilizes an open loop means for allowing the magnetic field winding set to generate sequential excitation for driving the rotary part, so that there is a shortage of the mentioned structure that each switched DC electric machine having conduction ring and brush requires an individual electromechanical control unit.